1. Field of the Invention
The present invention generally relates to remote control systems and, more particularly, to controls and circuits for solenoid operated remote control sprinkler valves used in irrigation systems.
2. Background of the Invention
Large areas of land which are grass covered and landscaped require attention and maintenance on a scheduled basis. Areas that are used regularly, for example for recreation, such as golf courses, require special care including watering on a time controlled schedule. Irrigation and watering is usually done by the use of a sprinkler system which necessarily includes a large number of sprinklers having the associated piping substantially permanently installed and being controlled from a remote location. A golf course or similar large area, may require an irrigation system having several hundred sprinklers, miles of piping and, in the case of sprinklers having remotely controlled electro-mechanically operated valves, such as solenoid operated valves, miles of electrical wiring as well.
An irrigation system of their general type is shown and described in U.S. Pat. No. 4,244,022 to Kendall. A sprinkler system specifically for use on parkways and other green strips which require periodic watering but infrequent maintenance of other sorts is shown and described in U.S. Pat. No. 3,911,955 to Link. Each sprinkler valve includes an on and an off solenoid for opening and closing the valve. This system is battery operated to eliminate the cost of laying power lines. It is timer controlled, includes a timing switch for each sprinkler and requires three wires to connect each sprinkler valve to its timer switch. U.S. Pat. No. 3,951,339 to DuFresne shows an irrigation system comprising a central sequencing control station for controlling remote valve stations. Two wires are connected to each remote station for electrically actuating the valves.
A grounding arrangement for a sprinkler system that is programmed by a microprocessor and clock is disclosed in U.S. Pat. No. 1,215,382 to Davis. This is also a system with solenoid type sprinkler valves, each of which may be operated by either a common control wire, or as shown in the patent, an individual wire; however, in this patent the grounding arrangement requires a common ground wire to be connected to each solenoid. Another patent directed to controlling watering systems is U.S. Pat. No. 4,333,490 to Enter, Sr. Ambient conditions such as humidity, light and the like can be factored into the timing cycle for control of watering.
U S. Pat. No. 4,423,484 to Hamilton relates to a battery operated programmable control system using bi-stable solenoids, each of which requires three connecting wires including the ground wire. The auxiliary switching circuit described in U.S. Pat. No. 4,661,719 to Burchfiel et al. is intended for use in irrigation systems having solenoid controlled valves and is especially adapted to provide an add-on or repair device for such systems. This patent is also notable for the discussion contained in the introductory paragraphs relating to sprinkler systems maintenance and repair costs. Other patents of interest that show circuits for controlling solenoid operation include U.S. Pat. No. 4,173,031 to Leichle and U.S. Pat. No. 4,161,320 to Herran. The former shows a device using a current program to control solenoids independently, while the latter selectively controls operations of solenoids by a switching circuit.
As noted above, quantities of electrical wire are needed for installations in which solenoid operated devices, such as valves, which are remotely controlled, are employed. The cost of laying power lines is referred to in U.S. Pat. No. 3,911,955 to Link as the basis for using battery power for control and operation in some areas. Further, in U.S. Pat. No. 4,661,719 to Burchfiel et al., reference is made to the high cost of pulling and replacing wire from which it follows that initial installations of wiring in accordance with current practice are very substantial. The systems disclosed in the patents discussed above as well as those in actual use are multi-wire systems or at best use one conductor and a common ground for each solenoid operating a sprinkler valve.